1. Field of the Invention
The present invention relates to a method for adjusting sensitivity of a pattern inspection apparatus which detects defects or foreign objects in a pattern of a photomask substrate or a semiconductor substrate utilized for manufacturing a semiconductor device.
2. Description of the Background Art
In a pattern inspection apparatus for detecting defective part in a pattern of a semiconductor wafer, a liquid crystal panel, a photomask or the like, a plurality of inspection lights 101, 102 and 103 are used to reduce the inspection time, as shown in FIG. 11. A method has been employed in which these plurality of lights are directed to a plurality of different portions on an inspected surface 122 of a substrate 150 of aforementioned device, the photomask or the like, to proceed with the inspection concurrently. In this inspection method, optical system elements such as an objective lens, an imaging element and the like are provided for each of the plurality of inspection lights 101, 102 and 103 which are output from the inspection apparatus. As such, each optical system needs to be adjusted to provide identical detection sensitivity for every light.
When adjusting each optical system, conventionally, only one of the inspection lights is driven to test its sensitivity, while the rest of inspection lights are shielded. Specifically, one inspection light scans pattern region 122 of a sensitivity adjusting substrate 110 to check its detection sensitivity. Next, only one of the rest of inspection lights is driven in a similar manner to check its detection sensitivity, and then these results are compared to be adjusted to the same level.
According to the above method for checking the sensitivity, the sensitivity check must be performed for each inspection light and thus requires considerable time for checking and adjusting sensitivity. Additionally, when a plurality of lights are provided, not every inspection light may be able to scan the identical portion of the inspected surface. In such a case, the inspected substrate may require to be, for example, rotated to change its direction. This rotation, however, changes the direction of the pattern of the inspected region, i.e., the direction of the defects or foreign objects to be detected. This rotation fluctuates a reflecting light or a scattering light for detection, hence hinders checking the correct limitation of detection sensitivity and to adjust the detection sensitivity for each inspection light.
Conventionally, as a sensitivity correction mask for a foreign objects inspection apparatus, a mask for improving identification of foreign objects has been disclosed (for example, Japanese Patent Laying-Open Nos. 11-84630 and 7-120404). On the other hand, a technique for efficiently adjusting sensitivity of optical systems associated with a plurality of inspection lights has never been disclosed.
The object of the present invention is to provide a sensitivity adjusting method for a pattern inspection apparatus, which performs inspection of patterns formed on a device or a photomask with a plurality of inspection lights, for efficiently and precisely checking and adjusting each of the optical systems associated with the inspection lights.
The sensitivity adjusting method for the pattern inspection apparatus according to the present invention is for adjusting the sensitivity of the pattern inspection apparatus inspecting patterns on a device formed during manufacture thereof, with a plurality of inspection lights. The present method includes the steps of preparing sensitivity adjusting substrate divided into a plurality of regions to which identical reference patterns are respectively provided, and scanning reference patterns with the plurality of inspection lights making one of said plurality of inspection lights respectively correspond to one of said reference patterns, after attaching to the sensitivity adjusting substrate to the pattern inspection apparatus.
With this configuration, a plurality of inspection lights can scan the identical reference patterns in respective region to obtain sensitivity information of respective optical systems associated with the inspection lights. As a result, efficiency is improved when checking the inspection sensitivity for a photomask or the like and adjusting the sensitivity. The aforementioned patterns on a device formed during manufacture thereof refers to the patterns formed on a various types of devices formed on a semiconductor substrate, specifically various types of semiconductor devices or liquid crystal panels or the like, and photomask patterns for forming such devices.
Further, base patterns may be formed by a semi-transparent film and programmed defects (i.e., defects deliberately formed for checking sensitivity) may be formed by transparent portions, such as gaps left by removing the semi-transparent film. Since the programmed defects are provided as such gaps, sensitivity of detecting foreign objects can be checked quantitatively.